// Aleth: Ethereum C++ client, tools and libraries.
// Copyright 2013-2019 Aleth Authors.
// Licensed under the GNU General Public License, Version 3.

/// @file
/// Recursive Linear-Prefix serialization / deserialization.
#pragma once

#include "Exceptions.h"
#include "FixedHash.h"
#include "vector_ref.h"

#include <array>
#include <exception>
#include <iomanip>
#include <iosfwd>
#include <vector>

namespace dev
{

class RLP;

template <class _T> struct intTraits { static const unsigned maxSize = sizeof(_T); };
template <> struct intTraits<u160> { static const unsigned maxSize = 20; };
template <> struct intTraits<u256> { static const unsigned maxSize = 32; };
template <> struct intTraits<bigint> { static const unsigned maxSize = ~(unsigned)0; };

static const byte c_rlpMaxLengthBytes = 8;
static const byte c_rlpDataImmLenStart = 0x80;
static const byte c_rlpListStart = 0xc0;

static const byte c_rlpDataImmLenCount = c_rlpListStart - c_rlpDataImmLenStart - c_rlpMaxLengthBytes;
static const byte c_rlpDataIndLenZero = c_rlpDataImmLenStart + c_rlpDataImmLenCount - 1;
static const byte c_rlpListImmLenCount = 256 - c_rlpListStart - c_rlpMaxLengthBytes;
static const byte c_rlpListIndLenZero = c_rlpListStart + c_rlpListImmLenCount - 1;

template <class T> struct Converter { static T convert(RLP const&, int) { BOOST_THROW_EXCEPTION(BadCast()); } };

/**
 * Class for interpreting Recursive Linear-Prefix Data.
 */
class RLP
{
public:
    /// Conversion flags
    enum
    {
        AllowNonCanon = 1,
        ThrowOnFail = 4,
        FailIfTooBig = 8,
        FailIfTooSmall = 16,
        Strict = ThrowOnFail | FailIfTooBig,
        VeryStrict = ThrowOnFail | FailIfTooBig | FailIfTooSmall,
        LaissezFaire = AllowNonCanon
    };

    using Strictness = int;

    /// Construct a null node.
    RLP() {}

    /// Construct a node of value given in the bytes.
    explicit RLP(bytesConstRef _d, Strictness _s = VeryStrict);

    /// Construct a node of value given in the bytes.
    explicit RLP(bytes const& _d, Strictness _s = VeryStrict): RLP(&_d, _s) {}

    /// Construct a node to read RLP data in the bytes given.
    RLP(byte const* _b, unsigned _s, Strictness _st = VeryStrict): RLP(bytesConstRef(_b, _s), _st) {}

    /// Construct a node to read RLP data in the string.
    explicit RLP(std::string const& _s, Strictness _st = VeryStrict): RLP(bytesConstRef((byte const*)_s.data(), _s.size()), _st) {}

    /// The bare data of the RLP.
    bytesConstRef data() const { return m_data; }

    /// @returns true if the RLP is non-null.
    explicit operator bool() const { return !isNull(); }

    /// No value.
    bool isNull() const { return m_data.size() == 0; }

    /// Contains a zero-length string or zero-length list.
    bool isEmpty() const { return !isNull() && (m_data[0] == c_rlpDataImmLenStart || m_data[0] == c_rlpListStart); }

    /// String value.
    bool isData() const { return !isNull() && m_data[0] < c_rlpListStart; }

    /// List value.
    bool isList() const { return !isNull() && m_data[0] >= c_rlpListStart; }

    /// Integer value. Must not have a leading zero.
    bool isInt() const;

    /// @returns the number of items in the list, or zero if it isn't a list.
    size_t itemCount() const { return isList() ? items() : 0; }
    size_t itemCountStrict() const { if (!isList()) BOOST_THROW_EXCEPTION(BadCast()); return items(); }

    /// @returns the number of bytes in the data, or zero if it isn't data.
    size_t size() const { return isData() ? length() : 0; }
    size_t sizeStrict() const { if (!isData()) BOOST_THROW_EXCEPTION(BadCast()); return length(); }

    /// Equality operators; does best-effort conversion and checks for equality.
    bool operator==(char const* _s) const { return isData() && toString() == _s; }
    bool operator!=(char const* _s) const { return isData() && toString() != _s; }
    bool operator==(std::string const& _s) const { return isData() && toString() == _s; }
    bool operator!=(std::string const& _s) const { return isData() && toString() != _s; }
    template <unsigned _N> bool operator==(FixedHash<_N> const& _h) const { return isData() && toHash<_N>() == _h; }
    template <unsigned _N> bool operator!=(FixedHash<_N> const& _s) const { return isData() && toHash<_N>() != _s; }
    bool operator==(unsigned const& _i) const { return isInt() && toInt<unsigned>() == _i; }
    bool operator!=(unsigned const& _i) const { return isInt() && toInt<unsigned>() != _i; }
    bool operator==(u256 const& _i) const { return isInt() && toInt<u256>() == _i; }
    bool operator!=(u256 const& _i) const { return isInt() && toInt<u256>() != _i; }
    bool operator==(bigint const& _i) const { return isInt() && toInt<bigint>() == _i; }
    bool operator!=(bigint const& _i) const { return isInt() && toInt<bigint>() != _i; }

    /// Subscript operator.
    /// @returns the list item @a _i if isList() and @a _i < listItems(), or RLP() otherwise.
    /// @note if used to access items in ascending order, this is efficient.
    RLP operator[](size_t _i) const;

    using element_type = RLP;

    /// @brief Iterator class for iterating through items of RLP list.
    class iterator
    {
        friend class RLP;

    public:
        using value_type = RLP;
        using element_type = RLP;

        iterator& operator++();
        iterator operator++(int) { auto ret = *this; operator++(); return ret; }
        RLP operator*() const { return RLP(m_currentItem); }
        bool operator==(iterator const& _cmp) const { return m_currentItem == _cmp.m_currentItem; }
        bool operator!=(iterator const& _cmp) const { return !operator==(_cmp); }

    private:
        iterator() {}
        iterator(RLP const& _parent, bool _begin);

        size_t m_remaining = 0;
        bytesConstRef m_currentItem;
    };

    /// @brief Iterator into beginning of sub-item list (valid only if we are a list).
    iterator begin() const { return iterator(*this, true); }

    /// @brief Iterator into end of sub-item list (valid only if we are a list).
    iterator end() const { return iterator(*this, false); }

    template <class T> inline T convert(int _flags) const;

    /// Best-effort conversion operators.
    explicit operator std::string() const { return toString(); }
    explicit operator bytes() const { return toBytes(); }
    explicit operator uint8_t() const { return toInt<uint8_t>(); }
    explicit operator uint16_t() const { return toInt<uint16_t>(); }
    explicit operator uint32_t() const { return toInt<uint32_t>(); }
    explicit operator uint64_t() const { return toInt<uint64_t>(); }
    explicit operator u160() const { return toInt<u160>(); }
    explicit operator u256() const { return toInt<u256>(); }
    explicit operator bigint() const { return toInt<bigint>(); }
    template <unsigned N> explicit operator FixedHash<N>() const { return toHash<FixedHash<N>>(); }
    template <class T, class U> explicit operator std::pair<T, U>() const { return toPair<T, U>(); }
    template <class T> explicit operator std::vector<T>() const { return toVector<T>(); }
    template <class T> explicit operator std::set<T>() const { return toSet<T>(); }
    template <class T, size_t N> explicit operator std::array<T, N>() const { return toArray<T, N>(); }

    /// Converts to bytearray. @returns the empty byte array if not a string.
    bytes toBytes(int _flags = LaissezFaire) const { if (!isData()) { if (_flags & ThrowOnFail) BOOST_THROW_EXCEPTION(BadCast()); else return bytes(); } return bytes(payload().data(), payload().data() + length()); }
    /// Converts to bytearray. @returns the empty byte array if not a string.
    bytesConstRef toBytesConstRef(int _flags = LaissezFaire) const { if (!isData()) { if (_flags & ThrowOnFail) BOOST_THROW_EXCEPTION(BadCast()); else return bytesConstRef(); } return payload().cropped(0, length()); }
    /// Converts to string. @returns the empty string if not a string.
    std::string toString(int _flags = LaissezFaire) const { if (!isData()) { if (_flags & ThrowOnFail) BOOST_THROW_EXCEPTION(BadCast()); else return std::string(); } return payload().cropped(0, length()).toString(); }
    /// Converts to string. @throws BadCast if not a string.
    std::string toStringStrict() const { return toString(Strict); }

    template <class T>
    std::vector<T> toVector(int _flags = LaissezFaire) const
    {
        std::vector<T> ret;
        if (isList())
        {
            ret.reserve(itemCount());
            for (auto const& i: *this)
                ret.push_back(i.convert<T>(_flags));
        }
        else if (_flags & ThrowOnFail)
            BOOST_THROW_EXCEPTION(BadCast());
        return ret;
    }

    template <class T>
    std::set<T> toSet(int _flags = LaissezFaire) const
    {
        std::set<T> ret;
        if (isList())
            for (auto const& i: *this)
                ret.insert(i.convert<T>(_flags));
        else if (_flags & ThrowOnFail)
            BOOST_THROW_EXCEPTION(BadCast());
        return ret;
    }

    template <class T>
    std::unordered_set<T> toUnorderedSet(int _flags = LaissezFaire) const
    {
        std::unordered_set<T> ret;
        if (isList())
            for (auto const& i: *this)
                ret.insert(i.convert<T>(_flags));
        else if (_flags & ThrowOnFail)
            BOOST_THROW_EXCEPTION(BadCast());
        return ret;
    }

    template <class T, class U>
    std::pair<T, U> toPair(int _flags = Strict) const
    {
        std::pair<T, U> ret;
        if (itemCountStrict() != 2)
        {
            if (_flags & ThrowOnFail)
                BOOST_THROW_EXCEPTION(BadCast());
            else
                return ret;
        }
        ret.first = (*this)[0].convert<T>(_flags);
        ret.second = (*this)[1].convert<U>(_flags);
        return ret;
    }

    template <class T, size_t N>
    std::array<T, N> toArray(int _flags = LaissezFaire) const
    {
        if (itemCount() != N)
        {
            if (_flags & ThrowOnFail)
                BOOST_THROW_EXCEPTION(BadCast());
            else
                return std::array<T, N>();
        }
        std::array<T, N> ret;
        for (size_t i = 0; i < N; ++i)
            ret[i] = operator[](i).convert<T>(_flags);
        return ret;
    }

    /// Converts to int of type given; if isData(), decodes as big-endian bytestream. @returns 0 if not an int or data.
    template <class _T = unsigned> _T toInt(int _flags = Strict) const
    {
        requireGood();
        if ((!isInt() && !(_flags & AllowNonCanon)) || isList() || isNull())
        {
            if (_flags & ThrowOnFail)
                BOOST_THROW_EXCEPTION(BadCast());
            else
                return 0;
        }

        auto p = payload();
        if (p.size() > intTraits<_T>::maxSize && (_flags & FailIfTooBig))
        {
            if (_flags & ThrowOnFail)
                BOOST_THROW_EXCEPTION(BadCast());
            else
                return 0;
        }

        return fromBigEndian<_T>(p);
    }

    int64_t toPositiveInt64(int _flags = Strict) const
    {
        int64_t i = toInt<int64_t>(_flags);
        if ((_flags & ThrowOnFail) && i < 0)
            BOOST_THROW_EXCEPTION(BadCast());
        return i;
    }

    template <class _N> _N toHash(int _flags = Strict) const
    {
        requireGood();
        auto p = payload();
        auto l = p.size();
        if (!isData() || (l > _N::size && (_flags & FailIfTooBig)) || (l < _N::size && (_flags & FailIfTooSmall)))
        {
            if (_flags & ThrowOnFail)
                BOOST_THROW_EXCEPTION(BadCast());
            else
                return _N();
        }

        _N ret;
        size_t s = std::min<size_t>(_N::size, l);
        memcpy(ret.data() + _N::size - s, p.data(), s);
        return ret;
    }

    /// @returns the data payload. Valid for all types.
    bytesConstRef payload() const { auto l = length(); if (l > m_data.size()) BOOST_THROW_EXCEPTION(BadRLP()); return m_data.cropped(payloadOffset(), l); }

    /// @returns the theoretical size of this item as encoded in the data.
    /// @note Under normal circumstances, is equivalent to m_data.size() - use that unless you know it won't work.
    size_t actualSize() const;

private:
    /// Disable construction from rvalue
    explicit RLP(bytes const&&) {}

    /// Throws if is non-canonical data (i.e. single byte done in two bytes that could be done in one).
    void requireGood() const;

    /// Single-byte data payload.
    bool isSingleByte() const { return !isNull() && m_data[0] < c_rlpDataImmLenStart; }

    /// @returns the amount of bytes used to encode the length of the data. Valid for all types.
    unsigned lengthSize() const { if (isData() && m_data[0] > c_rlpDataIndLenZero) return m_data[0] - c_rlpDataIndLenZero; if (isList() && m_data[0] > c_rlpListIndLenZero) return m_data[0] - c_rlpListIndLenZero; return 0; }

    /// @returns the size in bytes of the payload, as given by the RLP as opposed to as inferred from m_data.
    size_t length() const;

    /// @returns the number of bytes into the data that the payload starts.
    size_t payloadOffset() const { return isSingleByte() ? 0 : (1 + lengthSize()); }

    /// @returns the number of data items.
    size_t items() const;

    /// @returns the size encoded into the RLP in @a _data and throws if _data is too short.
    static size_t sizeAsEncoded(bytesConstRef _data) { return RLP(_data, ThrowOnFail | FailIfTooSmall).actualSize(); }

    /// Our byte data.
    bytesConstRef m_data;

    /// The list-indexing cache.
    // Index of the last item accessed with operator[]
    mutable size_t m_lastIndex = (size_t)-1;
    // Offset of the next byte after last byte of m_lastItem
    mutable size_t m_lastEnd = 0;
    // Data of the last item accessed with operator[]
    mutable bytesConstRef m_lastItem;
};

template <> struct Converter<std::string> { static std::string convert(RLP const& _r, int _flags) { return _r.toString(_flags); } };
template <> struct Converter<bytes> { static bytes convert(RLP const& _r, int _flags) { return _r.toBytes(_flags); } };
template <> struct Converter<uint8_t> { static uint8_t convert(RLP const& _r, int _flags) { return _r.toInt<uint8_t>(_flags); } };
template <> struct Converter<uint16_t> { static uint16_t convert(RLP const& _r, int _flags) { return _r.toInt<uint16_t>(_flags); } };
template <> struct Converter<uint32_t> { static uint32_t convert(RLP const& _r, int _flags) { return _r.toInt<uint32_t>(_flags); } };
template <> struct Converter<uint64_t> { static uint64_t convert(RLP const& _r, int _flags) { return _r.toInt<uint64_t>(_flags); } };
template <> struct Converter<u160> { static u160 convert(RLP const& _r, int _flags) { return _r.toInt<u160>(_flags); } };
template <> struct Converter<u256> { static u256 convert(RLP const& _r, int _flags) { return _r.toInt<u256>(_flags); } };
template <> struct Converter<bigint> { static bigint convert(RLP const& _r, int _flags) { return _r.toInt<bigint>(_flags); } };
template <unsigned N> struct Converter<FixedHash<N>> { static FixedHash<N> convert(RLP const& _r, int _flags) { return _r.toHash<FixedHash<N>>(_flags); } };
template <class T, class U> struct Converter<std::pair<T, U>> { static std::pair<T, U> convert(RLP const& _r, int _flags) { return _r.toPair<T, U>(_flags); } };
template <class T> struct Converter<std::vector<T>> { static std::vector<T> convert(RLP const& _r, int _flags) { return _r.toVector<T>(_flags); } };
template <class T> struct Converter<std::set<T>> { static std::set<T> convert(RLP const& _r, int _flags) { return _r.toSet<T>(_flags); } };
template <class T> struct Converter<std::unordered_set<T>> { static std::unordered_set<T> convert(RLP const& _r, int _flags) { return _r.toUnorderedSet<T>(_flags); } };
template <class T, size_t N> struct Converter<std::array<T, N>> { static std::array<T, N> convert(RLP const& _r, int _flags) { return _r.toArray<T, N>(_flags); } };

template <class T> inline T RLP::convert(int _flags) const { return Converter<T>::convert(*this, _flags); }

/**
 * @brief Class for writing to an RLP bytestream.
 */
class RLPStream
{
public:
    /// Initializes empty RLPStream.
    RLPStream() {}

    /// Initializes the RLPStream as a list of @a _listItems items.
    explicit RLPStream(size_t _listItems) { appendList(_listItems); }

    ~RLPStream() {}

    /// Append given datum to the byte stream.
    RLPStream& append(unsigned _s) { return append(bigint(_s)); }
    RLPStream& append(u160 _s) { return append(bigint(_s)); }
    RLPStream& append(u256 _s) { return append(bigint(_s)); }
    RLPStream& append(bigint _s);
    RLPStream& append(bytesConstRef _s, bool _compact = false);
    RLPStream& append(bytes const& _s) { return append(bytesConstRef(&_s)); }
    RLPStream& append(std::string const& _s) { return append(bytesConstRef(_s)); }
    RLPStream& append(char const* _s) { return append(std::string(_s)); }
    template <unsigned N> RLPStream& append(FixedHash<N> _s, bool _compact = false, bool _allOrNothing = false) { return _allOrNothing && !_s ? append(bytesConstRef()) : append(_s.ref(), _compact); }

    /// Appends an arbitrary RLP fragment - this *must* be a single item unless @a _itemCount is given.
    RLPStream& append(RLP const& _rlp, size_t _itemCount = 1) { return appendRaw(_rlp.data(), _itemCount); }

    /// Appends a sequence of data to the stream as a list.
    template <class _T> RLPStream& append(std::vector<_T> const& _s) { return appendVector(_s); }
    template <class _T> RLPStream& appendVector(std::vector<_T> const& _s) { appendList(_s.size()); for (auto const& i: _s) append(i); return *this; }
    template <class _T, size_t S> RLPStream& append(std::array<_T, S> const& _s) { appendList(_s.size()); for (auto const& i: _s) append(i); return *this; }
    template <class _T> RLPStream& append(std::set<_T> const& _s) { appendList(_s.size()); for (auto const& i: _s) append(i); return *this; }
    template <class _T> RLPStream& append(std::unordered_set<_T> const& _s) { appendList(_s.size()); for (auto const& i: _s) append(i); return *this; }
    template <class T, class U> RLPStream& append(std::pair<T, U> const& _s) { appendList(2); append(_s.first); append(_s.second); return *this; }

    /// Appends a list.
    RLPStream& appendList(size_t _items);
    RLPStream& appendList(bytesConstRef _rlp);
    RLPStream& appendList(bytes const& _rlp) { return appendList(&_rlp); }
    RLPStream& appendList(RLPStream const& _s) { return appendList(&_s.out()); }

    /// Appends raw (pre-serialised) RLP data. Use with caution.
    RLPStream& appendRaw(bytesConstRef _rlp, size_t _itemCount = 1);
    RLPStream& appendRaw(bytes const& _rlp, size_t _itemCount = 1) { return appendRaw(&_rlp, _itemCount); }

    /// Shift operators for appending data items.
    template <class T> RLPStream& operator<<(T _data) { return append(_data); }

    /// Clear the output stream so far.
    void clear() { m_out.clear(); m_listStack.clear(); }

    /// Read the byte stream.
    bytes const& out() const { if(!m_listStack.empty()) BOOST_THROW_EXCEPTION(RLPException() << errinfo_comment("listStack is not empty")); return m_out; }

    /// Invalidate the object and steal the output byte stream.
    bytes&& invalidate() { if(!m_listStack.empty()) BOOST_THROW_EXCEPTION(RLPException() << errinfo_comment("listStack is not empty")); return std::move(m_out); }

    /// Swap the contents of the output stream out for some other byte array.
    void swapOut(bytes& _dest) { if(!m_listStack.empty()) BOOST_THROW_EXCEPTION(RLPException() << errinfo_comment("listStack is not empty")); swap(m_out, _dest); }

private:
    void noteAppended(size_t _itemCount = 1);

    /// Push the node-type byte (using @a _base) along with the item count @a _count.
    /// @arg _count is number of characters for strings, data-bytes for ints, or items for lists.
    void pushCount(size_t _count, byte _offset);

    /// Push an integer as a raw big-endian byte-stream.
    template <class _T> void pushInt(_T _i, size_t _br)
    {
        m_out.resize(m_out.size() + _br);
        byte* b = &m_out.back();
        for (; _i; _i >>= 8)
            *(b--) = toUint8(_i);
    }

    /// Our output byte stream.
    bytes m_out;

    std::vector<std::pair<size_t, size_t>> m_listStack;
};

template <class _T> void rlpListAux(RLPStream& _out, _T _t) { _out << _t; }
template <class _T, class ... _Ts> void rlpListAux(RLPStream& _out, _T _t, _Ts ... _ts) { rlpListAux(_out << _t, _ts...); }

/// Export a single item in RLP format, returning a byte array.
template <class _T> bytes rlp(_T _t) { return (RLPStream() << _t).out(); }

/// Export a list of items in RLP format, returning a byte array.
inline bytes rlpList() { return RLPStream(0).out(); }
template <class ... _Ts> bytes rlpList(_Ts ... _ts)
{
    RLPStream out(sizeof ...(_Ts));
    rlpListAux(out, _ts...);
    return out.out();
}

/// The empty string in RLP format.
extern bytes RLPNull;

/// The empty list in RLP format.
extern bytes RLPEmptyList;

/// Human readable version of RLP.
std::ostream& operator<<(std::ostream& _out, dev::RLP const& _d);

}
